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Unitarity of black hole evaporation in final-state projection models

Lloyd, Seth and Preskill, John (2014) Unitarity of black hole evaporation in final-state projection models. Journal of High Energy Physics, 2014 (8). Art. No. 126. ISSN 1126-6708. doi:10.1007/JHEP08(2014)126.

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Almheiri et al. have emphasized that otherwise reasonable beliefs about black hole evaporation are incompatible with the monogamy of quantum entanglement, a general property of quantum mechanics. We investigate the final-state projection model of black hole evaporation proposed by Horowitz and Maldacena, pointing out that this model admits cloning of quantum states and polygamous entanglement, allowing unitarity of the evaporation process to be reconciled with smoothness of the black hole event horizon. Though the model seems to require carefully tuned dynamics to ensure exact unitarity of the black hole S-matrix, for a generic final-state boundary condition the deviations from unitarity are exponentially small in the black hole entropy; furthermore observers inside black holes need not detect any deviations from standard quantum mechanics. Though measurements performed inside old black holes could potentially produce causality-violating phenomena, the computational complexity of decoding the Hawking radiation may render the causality violation unobservable. Final-state projection models illustrate how inviolable principles of standard quantum mechanics might be circumvented in a theory of quantum gravity.

Item Type:Article
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Additional Information:© 2014 The Authors. Published for SISSA by Springer. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. Article funded by SCOAP3. Received: September 25, 2013; Revised: July 11, 2014; Accepted: July 24, 2014; Published: August 21, 2014. We gratefully acknowledge very valuable discussions with Alexei Kitaev. SL thanks Max Tegmark for helpful discussions, and JP thanks Raphael Bousso, Daniel Harlow, Juan Maldacena, Joe Polchinski, and Douglas Stanford for inspiring discussions and correspondence regarding final-state projection models. JP appreciates many helpful interactions with other participants at the August 2013 KITP workshop “Black Holes: Complementarity, Fuzz, or Fire”, and we also benefited from comments on the manuscript from Don Marolf and Douglas Stanford. The research of SL was supported in part by DARPA, by AFOSR, by the ARO under a MURI program, and by Jeffrey Epstein. The research of JP was supported in part by NSF, ARO, and DOE. The Institute for Quantum Information and Matter (IQIM) is an NSF Physics Frontiers Center with support from the Gordon and Betty Moore Foundation.
Group:Caltech Theory, Institute for Quantum Information and Matter
Funding AgencyGrant Number
Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Army Research Office (ARO)UNSPECIFIED
Jeffrey EpsteinUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Institute for Quantum Information and Matter (IQIM)UNSPECIFIED
NSF Physics Frontiers CenterUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:Black Holes, Spacetime Singularities
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CALT 68-2856
Issue or Number:8
Record Number:CaltechAUTHORS:20140611-133437673
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Official Citation:Lloyd, S. & Preskill, J. J. High Energ. Phys. (2014) 2014: 126. doi:10.1007/JHEP08(2014)126
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46212
Deposited By: Joy Painter
Deposited On:11 Jun 2014 20:55
Last Modified:10 Nov 2021 17:22

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